Manager Forum

I have a 1985 Cadillac Eldorado with a 4100 in the shop that has a severe knck in the engine.

Engine is firing on all cylinders. Was not running at all when it came into the shop. Put new plugs in it and it fired right up, idles great, accelerates smoothly, but has a nasty knock. I'ver been all over it with my stethescope and it is definitely in the upper end.

Has anyone encountered this before? It sounds like a bent pushrod or something like that but like i said, it runs smooth.

older cattys that I have had with engine noise some were from wrist pin noise which can sound upper engine at times.
I have also seen my fair share of cam lobes wore down. At idle it will run well. At higher rpms it will float
the valve train, back fire, pop threw the t/b. It being a wet sleaved engine you could also have a cyl. caseing
wore out. depending on how deep the knock sounds. good luck

Get ya some Mopar Combustion Chamber Cleaner and use it following the directions. I have used it on many occasions to clear up a top engine knock...HTH, Jeff

Possibly a carbon issue but i'm leaning towards a bad wrist pin. Years ago i would short each cylinder until the noise changed and if it did change case closed it was a wrist pin. If not it could be carbon. Another thing common on these was the crank pulley rattling. I've seen cracked fly wheels sound like an engine noise. These would crack right around the bolts and would sound like a jack hammer. Good luck.

I have had rockers brake on them and the 4.5

Was it the rockers or the aluminum rocker retainers? I seem to remember spending a lot of time swearing and wriggling valve covers off to replace retainers and the lower oilers. I think they were oilers. Again appearing through the fog.

it was a whole side they are mounted on a base.

Yep, getting clearer now. Wasn't it an aluminum galley rail for oiling.

Yea and they would break all the time. Hell i still have one in my tool box.LOL